In recent years, as candidates for post-liquid crystal displays and post-plasma displays, research and development are being extensively undertaken in relation to self-luminous displays represented by organic EL displays. The current organic EL displays are of two types: One is a low molecular weight type organic EL display in which a low molecular weight organic compound is used in a light emitting layer; the other is a high molecular weight type organic EL device in which a high molecular weight organic compound is used.
At present, for their high light emission efficiency, long life and the like, development of low molecular weight type EL displays in which a light emitting layer is prepared by using vacuum process such as vacuum deposition is ahead. However, the organic light emitting layer of the high molecular weight type EL display can be prepared by the wet-process such as the ink-jet method or the gravue printing method. Therefore, the productivity of the high molecular weight type organic EL display is much higher than that of the low molecular weight type organic EL display.
In the manufacturing of the high molecular weight type organic EL display, generally, for providing an organic light emitting material on the electrode, a barrier wall (hereinafter referred to as “bank”) surrounding the electrode is formed and an composition containing an organic light emitting material is applied to the region defined by the bank. The bank was usually formed by patterning a layer of the bank material applied on the substrate by the photolithography method. In addition, there is also a known technology to control the wettability of the bank by providing a layer made of silicon oxide between the bank and the substrate.
In addition, in the organic EL device, typically a hole injection layer is arranged between the anode and the organic light emitting layer. The hole injection layer has a function to support the injection of holes from the anode to the organic light emitting layer. In recent years, it was discovered that metal oxides such as tungsten oxide can be used as the material of the hole injection layer (See, for example, Patent Document 2,)
Patent Document 1: Japanese Patent No. 3743630
Patent Document 2: Japanese Patent Application Laid-Open No. 2006-114928